The present invention relates generally to a device for reading a binary-coded magnetic recording and more particularly to a mechanism for modulating the signal produced by a magnetic recording reading head to substantially reduce distortion.
The presently known devices for reading a magnetic recording coded in binary language generally include a reading head, a differentiator operating on the signal provided by the reading head, a digitizer and, in most cases, a preamplifier and amplifier. Thus, the reading signal is amplified, differentiated to improve its shape and digitized to reproduce the 0 and 1 binary code recorded on the recording support.
On the magnetic recording, the binary 0 and 1 are represented by different frequencies of magnetic flux polarity reversals. For example, the 0 can be associated with a reversal frequency of one half of that corresponding to the 1. Thus, the magnetic domain of the support associated with a 0 has, with respect to the reading head, a length double that of the magnetic domain corresponding to a 1. Theoretically, the 0's and 1's should, therefore, be clearly distinguishable since one is represented by pulses of duration different, e.g., double, that of the other.
However, in reality the reading signal provided by the reading head is highly distorted in amplitude and phase. This is due to the inherent characteristics of the reading head and magnetic support, as well as the distance which separates them. As a result, pulses representing 0 and 1 are often confused, such that the output signal of the digitizer contains numerous errors.